Atomic layer doping apparatus and method

ABSTRACT

An improved atomic layer doping apparatus is disclosed as having multiple doping regions in which individual monolayer species are first deposited and then dopant atoms contained therein are diffused into the substrate. Each doping region is chemically separated from adjacent doping regions. A loading assembly is programmed to follow pre-defined transfer sequences for moving semiconductor substrates into and out of the respective adjacent doping regions. According to the number of doping regions provided, a plurality of substrates could be simultaneously processed and run through the cycle of doping regions until a desired doping profile is obtained.

FIELD OF THE INVENTION

[0001] The present invention relates to the field of semiconductorintegrated circuits and, in particular, to an improved method for dopingwafers.

BACKGROUND OF THE INVENTION

[0002] Incorporation of dopants or chosen impurities into asemiconductor material, commonly known as doping, is well known in theart. Thermal diffusion and ion implantation are two methods currentlyused to introduce a controlled amount of dopants into selected regionsof a semiconductor material.

[0003] Doping by thermal diffusion is a two-step process. In the firststep, called predeposition, the semiconductor is either exposed to a gasstream containing excess dopant at low temperature to obtain a surfaceregion saturated with the dopant, or a dopant is diffused into a thinsurface layer from a solid dopant source coated onto the semiconductorsurface. The predeposition step is followed by the drive-in step, duringwhich the semiconductor is heated at high temperatures in an inertatmosphere so that the dopant in the thin surface layer of thesemiconductor is diffused into the interior of the semiconductor, andthus the predeposited dopant atoms are redistributed to a desired dopingprofile.

[0004] Ion implantation is preferred over thermal diffusion because ofthe capability of ion implantation to control the number of implanteddopant atoms, and because of its speed and reproducibility of the dopingprocess. The ion implantation process employs ionized-projectile atomsthat are introduced into solid targets, such as a semiconductorsubstrate, with enough kinetic energy (3 to 500 KeV) to penetrate beyondthe surface regions. A typical ion implant system uses a gas source ofdopant, such as, BF₃, PF₃, SbF₃, or AsH₃, for example, which isenergized at a high potential to produce an ion plasma containing dopantatoms. An analyzer magnet selects only the ion species of interest andrejects the rest of species. The desired ion species are then injectedinto an accelerator tube, so that the ions are accelerated to a highenough velocity to acquire a threshold momentum to penetrate the wafersurface when they are directed to the wafers.

[0005] Although ion implantation has many advantages, such as theability to offer precise dopant concentrations, for example, for siliconof about 10¹⁴ to 10²¹ atoms/cm³, there are various problems associatedwith this doping method. For example, a major drawback for ionimplantation is the radiation damage, which occurs because of thebombardment involved with heavy particles and further affects theelectrical properties of the semiconductor. The most common radiationdamage is the vacancy-interstitial defect, which occurs when an incomingdopant ion knocks substrate atoms from a lattice site and the newlydislocated atoms rest in a non-lattice position. Further, most of thedoping atoms are not electrically active right after implantation mainlybecause the dopant atoms do not end up on regular, active lattice sites.By a suitable annealing method, however, the crystal lattice could befully restored and the introduced dopant atoms are brought toelectrically active lattice sites by diffusion.

[0006] Ion channeling is another drawback of ion implantation that couldalso change the electrical characteristics of a doped semiconductor. Ionchanneling occurs when the major axis of the crystal wafer contacts theion beam, and when ions travel down the channels, reaching a depth asmuch as ten times the calculated depth. Thus, a significant amount ofadditional dopant atoms gather in the channels of the major axis. Ionchanneling can be minimized by several techniques, such as employing ablocking amorphous surface layer or misorienting the wafer so that thedopant ions enter the crystal wafer at angles different than a 90°angle. For example, misorientation of the wafer 3 to 7° off the majoraxis prevents the dopant ions from entering the channels. However, thesemethods increase the use of the expensive ionimplant machine and, thus,could be very costly for batch processing.

[0007] Another disadvantage of the conventional doping methods is theautodoping. After dopants are incorporated into a crystalline wafer toform various junctions, they undergo many subsequent processing stepsfor device fabrication. Although efforts are made to use low-temperatureprocessing techniques to minimize redistribution of incorporated dopantatoms, the dopants still redistribute during the course of furtherprocessing. For example, this redistribution of dopants becomesextremely important when an epitaxial film is grown over the top of thedoped area, particularly because of the high temperature required forepitaxial growth. At high temperatures, the dopant diffuses into thegrowing epitaxial film during the epitaxial growth, and this phenomenonis referred to as autodoping. This phenomenon also leads tounintentional doping of the film in between the doped regions, or intothe nondiffused substrate. For this, integrated circuit designers mustleave adequate room between adjacent regions to prevent the laterallydiffused regions from touching and shorting.

[0008] Furthermore, current doping systems today employ a batchprocessing, in which wafers are processed in parallel and at the sametime. An inherent disadvantage of batch processing is crosscontamination of the wafers from batch to batch, which further decreasesthe process control and repeatability, and eventually the yield,reliability and net productivity of the doping process.

[0009] Accordingly, there is a need for an improved doping system, whichwill permit minimal dopant redistribution, precise control of the numberof implanted dopants, higher commercial productivity and improvedversatility. There is also needed a new and improved doping system andmethod that will eliminate the problems posed by current batchprocessing technologies, as well as a method and system that will allowgreater uniformity and doping process control with respect to layerthickness necessary for increasing density of integration inmicroelectronics circuits.

SUMMARY OF THE INVENTION

[0010] The present invention provides an improved method and uniqueatomic layer doping system and method for wafer processing. The presentinvention contemplates an apparatus provided with multiple dopingregions in which individual monolayers of dopant species are firstdeposited by atomic layer deposition (ALD) on a wafer and then therespective dopants are diffused, by thermal reaction, for example, intothe wafer surface. Each doping region of the apparatus is chemicallyisolated from the other doping regions, for example, by an inert gascurtain. A robot is programmed to follow pre-defined transfer sequencesto move wafers into and out of respective doping regions for processing.Since multiple regions are provided, a multitude of wafers can besimultaneously processed in respective regions, each region depositingonly one monolayer dopant species and subsequently diffusing the dopantinto the wafer. Each wafer can be moved through the cycle of regionsuntil a desired doping concentration and profile is reached.

[0011] The present invention allows for the atomic layer doping ofwafers with higher commercial productivity and improved versatility.Since each region may be provided with a pre-determined set ofprocessing conditions tailored to one particular monolayer dopantspecies, cross contamination is also greatly reduced.

[0012] These and other features and advantages of the invention will beapparent from the following detailed description which is provided inconnection with the accompanying drawings, which illustrate exemplaryembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 illustrates a schematic top view of a multiple-chamberatomic layer doping apparatus according to the present invention.

[0014]FIG. 2 is a partial cross-sectional view of the atomic layerdoping apparatus of FIG. 1, taken along line 2-2′ and depicting twoadjacent doping regions according to a first embodiment of the presentinvention and depicting one wafer transfer sequence.

[0015]FIG. 3 is a partial cross-sectional view of the atomic layerdoping apparatus of FIG. 1, taken along line 2-2′ and depicting twoadjacent doping regions according to a second embodiment of the presentinvention.

[0016]FIG. 4 is a partial cross-sectional view of the atomic layerdoping apparatus of FIG. 2, depicting a physical barrier between twoadjacent doping chambers.

[0017]FIG. 5 is a schematic top view of a multiple-chamber atomic layerdoping apparatus according to the present invention and depicting asecond wafer transfer sequence.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In the following detailed description, reference is made tovarious exemplary embodiments of the invention. These embodiments aredescribed with sufficient detail to enable those skilled in the art topractice the invention, and it is to be understood that otherembodiments may be employed, and that structural and electrical changesmay be made without departing from the spirit or scope of the presentinvention.

[0019] The term “substrate” used in the following description mayinclude any semiconductor-based structure. Structure must be understoodto include silicon, silicon-on insulator (SOI), silicon-on sapphire(SOS), doped and undoped semiconductors, epitaxial layers of siliconsupported by a base semiconductor foundation, and other semiconductorstructures. The semiconductor need not be silicon-based. Thesemiconductor could be silicon-geranium, germanium, or gallium arsenide.When reference is made to substrate in the following description,previous process steps may have been utilized to form regions orjunctions in or on the base semiconductor or foundation.

[0020] The term “dopant” is intended to include not only elementaldopant atoms, but dopant atoms with other trace elements or in variouscombinations with other elements as known in the semiconductor art, aslong as such combinations retain the physical and chemical properties ofthe dopant atoms. The term “p-type dopant” used in the followingdescription may include any p-type impurity ions, such as zinc (Zn),magnesium (Mg), beryllium (Be), boron (B), gallium (Ga) or indium (In),among others. The term “n-type dopant” may include any n-type impurityions, such as silicon (Si), sulfur (S), tin (Sn), phosphorus (P),arsenic (As) or antimony (Sb), among others.

[0021] The present invention provides an atomic layer doping method andapparatus. As it will be described in more details below, the apparatusis provided with multiple doping regions in which individual monolayerdopant species are first deposited on a substrate and then dopant atomscorresponding to each of the monolayer species are diffused intorespective substrates. Each doping region is chemically separated fromthe adjacent doping regions. A robot is programmed to follow pre-definedtransfer sequences for moving wafers into and out of the respectiveadjacent doping regions. According to the number of doping regionsprovided, a multitude of substrates could be simultaneously processedand run through the cycle of different doping regions until a desireddoping concentration of a wafer surface is completed.

[0022] The present invention provides a simple and novel multi-chambersystem for atomic layer doping processing. Although the presentinvention will be described below with reference to the atomic layerdeposition of a dopant species Ax and the subsequent diffusion of itsdopant atoms into a wafer, it must be understood that the presentinvention has equal applicability for the formation of any dopedmaterial capable of being formed by atomic layer doping techniques usingany number of species, where each dopant species is deposited in areaction chamber dedicated thereto.

[0023] A schematic top view of a multiple-chamber atomic layer dopingapparatus 100 of the present invention is shown in FIG. 1. According toan exemplary embodiment of the present invention, doping regions 50 a,50 b, 52 a, 52 b, 54 a, and 54 b are alternately positioned around aloading mechanism 60, for example a robot. These doping regions may beany regions for the atomic layer doping treatment of substrates. Thedoping regions may be formed as cylindrical reactor chambers, 50 a, 50b, 52 a, 52 b, 54 a, and 54 b, in which adjacent chambers are chemicallyisolated from one another.

[0024] To facilitate wafer movement, and assuming that only onemonolayer of a dopant species Ax is to be deposited per cycle, thereactor chambers are arranged in pairs 50 a, 50 b; 52 a, 52b; 54 a, 54b. One such pair, 50 a, 50 b is shown in FIG. 2. While one of thereactor chambers of a pair, for example 50 a, deposits one monolayer ofthe dopant species Ax, the other reactor chamber of the pair, forexample 50 b, facilitates subsequent diffusion of the dopant atoms ofspecies Ax into the wafer to complete the doping process. The adjacentreactor chamber pairs are chemically isolated from one another, forexample by a gas curtain, which keeps the monolayer of dopant species Axin a respective region, for example 50 a, and which allows waferstreated in one reaction chamber, for example 50 a, to be easilytransported by the robot 60 to the other reaction chamber 50 b, and viceversa. Simultaneously, the robot can also move wafers between chambers52 a or 52 b, and 54 a and 54 b.

[0025] In order to chemically isolate the paired reaction chambers 50 a,50 b; 52 a, 52 b; and 54 a, 54 b, the paired reaction chambers show awall through which the wafers may pass, with the gas curtain acting ineffect as a chemical barrier preventing the gas mixture within onechamber, for example 50 a, from entering the paired adjacent chamber,for example 50 b.

[0026] It should be noted that, when a particular doping concentrationand/or profile is required, the robot can simply move wafers back andforth between the adjacent chambers, for example 50 a, 50 b, until thedesired doping profile and/or concentration of the wafer is obtained.

[0027] It should also be noted that, while two adjacent chambers havebeen illustrated for doping of a substrate using monolayers of dopantspecies Ax, one or more additional chambers, for example 50 c, 52 c, 54c, may also be used for deposition of additional respective monolayersof dopant species, such as By, for example, wit h the additionalchambers being chemically isolated from the chambers depositing the Axmonolayer dopant species in the same way the chambers for depositing theAx species are chemically isolated.

[0028] The loading assembly 60 of FIG. 1 may include an elevatormechanism along with a wafer supply mechanism. As well-known in the art,the supply mechanism may be further provided with clamps and pivot arms,so that a wafer 55 can be maneuvered by the robot and positionedaccording to the requirements of the atomic layer doping processingdescribed in more detail below.

[0029] Further referring to FIG. 1, a processing cycle for atomic layerdoping on a wafer 55 begins by selectively moving a first wafer 55, fromthe loading assembly 60 to the chamber reactor 50 a, in the direction ofarrow A₁ (FIG. 1). Similarly, a second wafer 55′ may be selectivelymoved by the loading assembly 60 to the chamber reactor 52 a, in thedirection of arrow A₂. Further, a third wafer 55″ is also selectivelymoved by the loading assembly 60 to the chamber reactor 54 a, in thedirection A₃. At this point, each of chambers 50 a, 52 a, 54 a are readyfor atomic layer deposition of a monolayer of a dopant species, forexample Ax.

[0030]FIG. 2 illustrates a cross-sectional view of the apparatus 100 ofFIG. 1, taken along line 2-2′. For simplicity, FIG. 2 shows only across-sectional view of adjacent reactor chambers 50 a and 50 b. Inorder to deposit an atomic monolayer on the wafer 55, the wafer 55 isplaced inside of the reactor chamber 50 a, which may be provided as aquartz or aluminum container 120. The wafer 55 is placed by the loadingassembly 60 (FIG. 1) onto a suscepter 140 a (FIG. 2), which in turn issituated on a heater assembly 150 a. Mounted on the upper wall of thereactor chamber 50 a is a dopant gas supply inlet 160 a, which isfurther connected to a dopant gas supply source 162 a for a first dopantgas precursor Ax. An exhaust outlet 180 a, connected to an exhaustsystem 182 a, is situated on the opposite wall from the dopant gassupply inlet 160 a.

[0031] The wafer 55 is positioned on top of the suscepter 140 a (FIG. 2)by the loading assembly 60, and then a first dopant gas precursor Ax issupplied into the reactor chamber 50 a through the dopant gas inlet 160a. The first dopant gas precursor Ax flows at a right angle onto thewafer 55 and reacts with its top substrate surface to form a firstmonolayer 210 a of the first dopant species Ax, by an atomic layerdeposition mechanism. Preferred gas sources of dopants are hydratedforms of dopant atoms such as arsine (AsH₃) and diborane (B₂H₆). Thesegases are mixed in different dilutions in pressurized containers, suchas the dopant gas supply source 162 a (FIG. 2), and connected directlyto the dopant gas inlets, such as the dopant gas inlet 160 a (FIG. 2).Gas sources offer the advantage of precise control through pressureregulators and are favored for deposition on larger wafers.

[0032] Alternatively, a liquid source of dopant such as chlorinated orbrominated compounds of the desired element may be used. When a liquidsource of dopant is used, a boron liquid source, for example borontribromide (BBr₃), or a phosphorous liquid source, for examplephosphorous oxychloride (POCl₃), may be held in temperature-controlledflasks over which an inert gas, such as nitrogen (N₂), is bubbledthrough the heated liquid, so that the gas becomes saturated with dopantatoms. The inert gas carries the dopant vapors through a gas tube andcreates a laminar flow of dopant atoms. A reaction gas is also requiredto create the elemental dopant form in the tube. For BBr₃, for example,the reaction gas is oxygen, which creates the boron trioxide (B₂O₃)which further deposits as a monolayer of boron trioxide on the surfaceof the wafer.

[0033] In any event, after the deposition of a monolayer of the firstdopant species Ax on the wafer surface 55, the processing cycle for thewafer 55 continues with the removal of the wafer 55 from the chamberreactor 50 a to the chamber reactor 50 b, in the direction of arrow B₁,as also illustrated in FIG. 1. After the deposition of the firstmonolayer 210 a of the first dopant species Ax, the wafer 55 is movedfrom the reactor chamber 50 a, through a gas curtain 300 (FIG. 2), tothe reactor chamber 50 b, by the loading assembly 60 (FIG. 1) and in thedirection of arrow B₁ of FIG. 2. It is important to note that the gascurtain 300 provides chemical isolation between adjacent depositionregions.

[0034] The loading assembly 60 moves the wafer 55 through the gascurtain 300, onto the suscepter 140 b situated in the reactor chamber 50b, which, in contrast with the reactor chamber 50 a, contains no dopantsource and no dopant species. A heater assembly 150 b is positionedunder the suscepter 140 b to facilitate the diffusion of the dopantatoms from the newly deposited first monolayer 210 a of the first dopantspecies Ax into the wafer 55. The heat from the heater assembly 150 bdrives the dopant atoms into the wafer 55 and further redistributes thedopant atoms from the first monolayer 210 a deeper into the wafer 55 toform a doped region 210 b of the first dopant species Ax. During thisstep, the surface concentration of dopant atoms is reduced and thedistribution of dopant atoms continues, so that a precise and shallowdoping distribution in the doped region 210 b of the wafer 55 isobtained. Accordingly, the depth of the doped region 210 b of the wafer55 is controlled, first, by the repeatability of the atomic layerdeposition for the monolayers of dopant species and, second, by thedegree of diffusion of dopants form the monolayers of dopant speciesinto the wafers.

[0035] Alternatively, a plasma of a non-reactive gas may be used tocomplete the diffusion of the dopant atoms into the doped region 210 bof the wafer 55. In this embodiment, a supply inlet 160 b (FIG. 2),which is further connected to a non-reactive gas supply source 162 b,for the plasma of the non-reactive gas, is mounted on the upper wall ofthe reactor chamber 50 b. An exhaust inlet 180 b, connected to anexhaust system 182 b, is further situated on the opposite wall to thenon-reactive gas supply inlet 160 b.

[0036] Next, the non-reactive gas By is supplied into the reactorchamber 50 b through the non-reactive gas inlet 160 b, the non-reactivegas By flowing at a right angle onto the deposited first monolayer 210 aof the first dopant species Ax. This way, particles of the non-reactivegas By “knock” the dopant atoms from the first monolayer 210 a of thefirst doping species Ax into the wafer 55 to form the doped region 210 bof the wafer 55.

[0037] Following the formation of the doped region 210 b of the wafer55, the process continues with the removal of the wafer 55 from thereactor chamber 50 b, through the gas curtain 300, and into the reactorchamber 50 a to continue the doping process. This process is repeatedcycle after cycle, with the wafer 55 traveling back and forth betweenthe reactor chamber 50 a, and the reactor chamber 50 b, to acquire thedesired doping profile of the region 210 b.

[0038] Once the desired doping profile of the wafer 55 has beenachieved, an anneal step in the atomic layer doping process is required,to restore any crystal damage and to electrically activate the dopantatoms. As such, annealing can be achieved by a thermal heating step.However, the anneal temperature must be preferably below the diffusiontemperature to prevent lateral diffusion of the dopants. Referring toFIG. 2, the anneal step could take place in the reactor chamber 50 b,for example, by controlling the heat from the heater assembly 150 b.Alternatively, the anneal step may take place into an adjacent reactorchamber, for example reactor chamber 52 a, depending on the processingrequirements and the desired number of wafers to be processed.

[0039] By employing chemically separate reactor chambers for thedeposition process of species Ax dopant and possibly others, the presentinvention has the major advantage of allowing different processingconditions, for example, deposition or diffusion temperatures, indifferent reactor chambers. This is important since the chemisorptionand reactivity requirements of the ALD process have specific temperaturerequirements, in accordance with the nature of the precursor gas.Accordingly, the apparatus of the present invention allows, for example,reactor chamber 50 a to be set to a different temperature than that ofthe reactor chamber 50 b. Further, each reactor chamber may be optimizedeither for improved chemisorption, reactivity or dopant conditions.

[0040] The configuration of the atomic layer doping apparatusillustrated above also improves the overall yield and productivity ofthe doping process, since each chamber could run a separate substrate,and therefore, a plurality of substrates could be run simultaneously ata given time. In addition, since each reactor chamber accommodates onlyone dopant species, cross-contamination from one wafer to another isgreatly reduced. Moreover, the production time can be decreased sincethe configuration of the apparatus of the present invention saves agreat amount of purging and reactor clearing time.

[0041] Of course, although the doping process was explained above onlywith reference to the first substrate 55 in the first chamber reactor 50a and the second chamber reactor 50 b, it is to be understood that sameprocessing steps are carried out simultaneously on the second and thirdwafers 55′, 55″ for their respective chamber reactors. Further, thesecond and third wafers 55′, 55 ′ are moved accordingly, in thedirections of arrows A₂, B₂ (corresponding to chamber reactors 52 a, 52b) and arrows A₃, B₃ (corresponding to chamber reactors 54 a, 54 b).Moreover, while the doping process was explained above with reference toonly one first substrate 55 for the first and second reactor chambers 50a, 50 b, it must be understood that the first and second reactorchambers 50 a, 50 b could also process another first substrate 55, in adirection opposite to that of processing the other first substrate. Forexample, if one first substrate 55 travels in the direction of arrow B₁(FIG. 2) the other first substrate 55 could travel in the oppositedirection of arrow B₁, that is from the second reactor chamber 50 b tothe first reactor chamber 50 a.

[0042] Assuming a specific doping concentration is desired on the wafer55, after the diffusion of the dopant atoms from the first monolayer 210a in the reactor chamber 50 b, the wafer 55 is then moved back by theassembly system 60 to the reactor chamber 50 a, where a second monolayerof the first dopant species Ax is next deposited over the firstmonolayer of the first dopant species Ax. The wafer 55 is further movedto the reactor chamber 50 b for the subsequent diffusion of the dopantatoms from the second monolayer of the first dopant species Ax. Thecycle continues until a desired doping concentration on the surface ofthe wafer 55 is achieved, and, thus, the wafer 55 travels back and forthbetween reactor chambers 50 a and 50 b. As explained above, the samecycle process applies to the other two wafers 55′, 55″ that areprocessed simultaneously in their respective reactor chambers.

[0043] Although the invention is described with reference to reactorchambers, any other type of doping regions may be employed, as long asthe wafer 55 is positioned under a flow of dopant source. The gascurtain 300 provides chemical isolation to all adjacent depositionregions. Thus, as illustrated in FIGS. 2-3, the gas curtain 300 isprovided between the two adjacent reactor chambers 50 a and 50 b so thatan inert gas 360, such as nitrogen, argon, or helium, for example, flowsthrough an inlet 260 connected to an inert gas supply source 362 to formthe gas curtain 300, which keeps the first dopant gas Ax and thenon-reactive gas By from flowing into adjacent reaction chambers. Anexhaust outlet 382 (FIG. 2) is further situated on the opposite wall tothe inert gas inlet 260. It must also be noted that the pressure of theinert gas 360 must be higher than that of the first dopant gas Ax andthat of the non-reactive gas By, so that the two doping gases Ax, By areconstrained by the gas curtain 300 to remain within their respectivereaction chambers.

[0044]FIG. 3 illustrates a cross-sectional view of the apparatus 100 ofFIG. 2, with same adjacent reactor chambers 50 a and 50 b, but in whichthe inert gas 360 shares the exhaust outlets 180 a and 180 b with thetwo doping gases Ax and By, respectively. Thus, the atomic layer dopingapparatus 100 may be designed so that the inert gas 360 of the gascurtain 300 could be exhausted through either one or both of the twoexhaust outlets 180 a and 180 b, instead of being exhausted through itsown exhaust outlet 382, as illustrated in FIG. 2.

[0045]FIG. 4 shows another alternate embodiment of the apparatus inwhich the gas curtain 300 separating adjacent chambers in FIGS. 2-3 isreplaced by a physical boundary, such as a wall 170 having a closeableopening 172. A door 174 (FIG. 4) can be used to open and close theopening 172 between the adjacent paired chambers 50 a, 50 b. This way,the wafer 55 can be passed between the adjacent chambers 50 a, 50 bthrough the open opening 172 by the robot 60, with the door 174 closingthe opening 172 during atomic layer doping processing.

[0046] Although the present invention has been described with referenceto only three semiconductor substrates processed at relatively the sametime in respective pairs of reaction chambers, it must be understoodthat the present invention contemplates the processing of any “n” numberof wafers in their corresponding “m” number of reactor chambers, where nand m are integers. Thus, in the example shown in FIG. 1, n=3 and m=6,providing an atomic layer doping apparatus with at least 6 reactionchambers that could process simultaneously 3 wafers for a repeatingtwo-step atomic layer doping using Ax as a dopant source and By as anon-reactive gas for diffusion. It is also possible to have n=2 and m=6where two wafers are sequentially transported to and processed in thereaction chambers for sequential doping with two species, for example,Ax and a second dopant species Cz, while employing the non-reactive gasBy to facilitate the diffusion of the dopant atoms Ax and Cz. Othercombinations are also possible. Thus, although the invention has beendescribed with the wafer 55 traveling back and forth from the reactorchamber 50 a to the reactor chamber 50 b with reference to FIG. 2, itmust be understood that, when more than two reactor chambers are usedfor doping with more than two monolayer species Ax, Cz, the wafer 55will be transported by the loading assembly 60 among all the reactionchambers in a sequence required to produce a desired doping profile.

[0047] Also, although the present invention has been described withreference to wafers 55, 55′ and 55″ being selectively moved by theloading assembly 60 to their respective reactor chambers 50 a and 50 b(for wafer 55), 52 a and 52 b (for wafer 55′), and 54 a and 54 b (forwafer 55″), it must be understood that each of the three above wafers ormore wafers could be sequentially transported to, and processed in, allthe reaction chambers of the apparatus 100. This way, each wafer couldbe rotated and moved in one direction only. Such a configuration isillustrated in FIG. 5, according to which a processing cycle for atomiclayer deposition on a plurality of wafers 55, for example, begins byselectively moving each wafer 55, from the loading assembly 60 to thechamber reactor 50 a, in the direction of arrow A₁ (FIG. 5), and thenfurther to the reactor chamber 50 b, 52 a, 52 b, 54 a, and 54 b. Onereaction chamber, for example 50 a, can serve as the initial chamber andanother, for example 54 b, as the final chamber. Each wafer 55 issimultaneously processed in a respective chamber and is movedsequentially through the chambers by the loading assembly 60, with thecycle continuing with wafers 55 traveling in one direction to all theremaining reactors chambers. Although this embodiment has been describedwith reference to a respective wafer in each chamber, it must beunderstood that the present invention contemplates the processing of any“n” number of wafers in corresponding “m” number of reactor chambers,where n and m are integers and n≦m. Thus, in the example shown in FIG.5, the ALD apparatus with 6 reaction chambers could processsimultaneously up to 6 wafers.

[0048] The above description illustrates preferred embodiments thatachieve the features and advantages of the present invention. It is notintended that the present invention be limited to the illustratedembodiments. Modifications and substitutions to specific processconditions and structures can be made without departing from the spiritand scope of the present invention. Accordingly, tie invention is not tobe considered as being limited by the foregoing description anddrawings, but is only limited by the scope of the appended claims.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. An atomic layer doping apparatus comprising: afirst atomic layer doping region for depositing a first dopant specieson a first substrate as a monolayer; a second atomic layer doping regionfor diffusing said first dopant species in said first substrate, saidfirst and second doping regions being chemically isolated from oneanother; and a loading assembly for moving said first substrate fromsaid first doping region to said second doping region, thereby enablingdeposition of a first atomic monolayer in said first doping region,followed by diffusion of said first atomic monolayer in said seconddoping region.
 2. The doping apparatus of claim 1, wherein said firstand second doping regions are adjacent to one another and chemicallyisolated.
 3. The doping apparatus of claim 2, wherein said first andsecond doping regions are chemically isolated from one another by a gascurtain.
 4. The doping apparatus of claim 3, wherein said gas curtain isformed of an inert gas.
 5. The doping apparatus of claim 2, wherein saidfirst and second doping regions are chemically isolated from one anotherby a physical barrier having a closeable opening through which saidloading assembly can move a substrate.
 6. The doping apparatus of claim1, wherein said loading assembly is further able to move said substratefrom said second doping region back to said first doping region.
 7. Thedoping apparatus of claim 1 further comprising a plurality of first andsecond atomic layer doping regions.
 8. The doping apparatus of claim 7,wherein said plurality of first and second doping regions are grouped inpairs of first and second doping regions, so that at least said firstsubstrate and a second substrate can be treated simultaneously inrespective pairs of first and second doping regions.
 9. The dopingapparatus of claim 8 further comprising a third pair of first and secondatomic layer doping regions for processing a third substrate in saidthird pair of first and second atomic layer doping regionssimultaneously with processing of said first and second substrates. 10.The doping apparatus of claim 7, wherein said loading assembly islocated at the center of said doping regions.
 11. The doping apparatusof claim 1 further comprising at least one third atomic layer dopingregion.
 12. The doping apparatus of claim 11, wherein said first,second, and third doping regions are adjacent to one another andchemically isolated.
 13. The doping apparatus of claim 12, wherein saidfirst, second, and third doping regions are chemically isolated from oneanother by a gas curtain.
 14. The doping apparatus of claim 13, whereinsaid gas curtain is formed of an inert gas.
 15. The doping apparatus ofclaim 11, wherein said first, second, and third doping regions arechemically isolated from one another by a physical barrier having acloseable opening through which said loading assembly can move asubstrate.
 16. The doping apparatus of claim 11, wherein said loadingassembly is further able to move sequentially said first substrate amongsaid first doping region, said second doping region, and said thirddoping region.
 17. The doping apparatus of claim 16, wherein saidloading assembly is further able to move sequentially another substrateamong said first doping region, said second doping region, and saidthird doping region.
 18. A method of operating an atomic layer dopingapparatus, said doping apparatus comprising a first doping region and asecond doping region, said first and second doping regions beingchemically isolated from one another, said method comprising the stepsof: positioning a wafer in said first doping region; introducing a firstdopant species into said first doping region and depositing said firstdopant species on said wafer as a first atomic monolayer; moving saidwafer from said first doping region to said second doping region; andintroducing dopants from said first atomic monolayer into said wafer insaid second doping region.
 19. The method of claim 18 further comprisingthe act of annealing said wafer after said act of introducing saiddopants into said wafer.
 20. The method of claim 18, wherein said act ofintroducing said dopants into said wafer includes diffusion of saiddopants.
 21. The method of claim 18, wherein said act of introducingsaid dopants into said wafer includes contacting said wafer with anon-reactive plasma.
 22. The method of claim 18 further comprising theact of moving said wafer back and forth between said first and seconddoping regions.
 23. The method of claim 18 further comprising the act ofmoving said wafer back to said first doping region and depositing saidfirst dopant species as a second atomic monolayer.
 24. The method ofclaim 18, wherein said first and second doping regions are adjacent toeach other.
 25. The method of claim 18 further comprising the act ofsimultaneously processing at least two wafers among said first andsecond doping regions and depositing a respective dopant species in eachof said doping regions.
 26. The method of claim 18, wherein said leasttwo wafers are sequentially moved among said first and second dopingregions.
 27. A method of conducting atomic layer doping comprising thesteps of: depositing a first atomic monolayer including atoms of adopant species on a substrate in a first doping region; moving saidsubstrate from said first doping region to a second doping region, whichis chemically isolated from said first doping region; and introducingsaid atoms of said dopant species into said wafer.
 28. The method ofclaim 27, wherein said act of depositing said first monolayer speciesfurther comprises introducing a first dopant species into said firstdoping region.
 29. The method of claim 27, wherein said act ofintroducing said atoms of said dopant species into said wafer furthercomprises introducing a non-reactive plasma into said second dopingregion and contacting said non-reactive plasma with said first atomicmonolayer species.
 30. The method of claim 27, wherein said act ofintroducing said atoms of said dopant species into said wafer furthercomprises heating said wafer so that said atoms diffuse into a surfaceregion of said wafer.
 31. The method of claim 27 further comprising theact of annealing said wafer.
 32. The method of claim 27 furthercomprising the act of moving said substrate back and forth between saidfirst and second doping regions.
 33. The method of claim 27, wherein aplurality of first and second doping regions are provided, and saidmethod further comprising depositing said first monolayer on respectivesubstrates and introducing atoms from said first monolayers intorespective substrates in respective pairs of first and second dopingregions, said first and second doping regions of each pair beingadjacent to one another.
 34. The method of claim 33, wherein a pluralityof substrates, each of said plurality of substrates residing inrespective regions, are moved sequentially from said first dopingregions to said second doping regions.
 35. A method of operating anatomic layer doping apparatus, said doping apparatus comprising aplurality of doping regions, said doping regions being chemicallyisolated from one another, said method comprising the steps of:positioning a plurality of wafers in respective doping regions;introducing a first dopant species into some of said plurality of dopingregions and depositing said first dopant species on at least one of saidplurality of wafers as a first atomic monolayer, said first atomicmonolayer comprising dopant atoms of said first dopant species; movingsaid plurality of wafers from said some of said plurality of dopingregions to other doping regions; and introducing a second gas speciesinto said other doping regions and contacting said second gas species onat least one of said plurality of wafers to introduce said dopant atomsinto said at least one of said plurality of wafers.
 36. The method ofclaim 35 further comprising the act of sequentially moving saidplurality of wafers through at least two of said plurality of dopingregions in accordance with a predefined pattern.
 37. The method of claim35, wherein said second gas species is a non-reactive plasma.
 38. Themethod of claim 35 further comprising the act of annealing said at leastone of said plurality of wafers.
 39. The method of claim 35 furthercomprising the act of sequentially moving said plurality of wafersthrough all said doping regions.
 40. The method of claim 35 furthercomprising the act of sequentially moving said plurality of wafersthrough predetermined regions of said doping regions.
 41. A method ofconducting atomic layer doping comprising the steps of: depositing afirst atomic monolayer including atoms of a first dopant species on asubstrate in a first doping region; moving said substrate from saidfirst doping region to a second doping region, which is chemicallyisolated from said first doping region, for depositing a secondmonolayer including atoms of a second dopant species on said substrate;and moving said substrate from said second doping regions to a thirddoping region, which is chemically isolated from said first and seconddoping regions, for introducing said atoms of said first and seconddopant species into said wafer.
 42. The method of claim 41, wherein saidact of introducing said atoms of said first and second dopant speciesinto said wafer further comprises introducing a non-reactive plasma intosaid third doping region and contacting said non-reactive plasma withsaid first and second atomic monolayer species.
 43. The method of claim41, wherein said act of introducing said atoms of said first and seconddopant species into said wafer further comprises heating said wafer sothat said atoms diffuse into a surface region of said wafer.
 44. Themethod of claim 41 further comprising the act of annealing said wafer.45. The method of claim 41 further comprising the act of sequentiallymoving said substrate back and forth between said first, second andthird doping regions.